Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B7/00—Radio transmission systems, i.e. using radiation field
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W74/00—Wireless channel access
  • H04W74/04—Scheduled access
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/1607—Details of the supervisory signal
  • H04L1/1685—Details of the supervisory signal the supervisory signal being transmitted in response to a specific request, e.g. to a polling signal
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1809—Selective-repeat protocols
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1829—Arrangements specially adapted for the receiver end
  • H04L1/1832—Details of sliding window management
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1867—Arrangements specially adapted for the transmitter end
  • H04L1/187—Details of sliding window management
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1867—Arrangements specially adapted for the transmitter end
  • H04L1/1874—Buffer management
  • H04L1/1877—Buffer management for semi-reliable protocols, e.g. for less sensitive applications like streaming video
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L1/00—Arrangements for detecting or preventing errors in the information received
  • H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
  • H04L1/16—Arrangements for detecting or preventing errors in the information received by using return channel in which the return channel carries supervisory signals, e.g. repetition request signals
  • H04L1/18—Automatic repetition systems, e.g. Van Duuren systems
  • H04L1/1867—Arrangements specially adapted for the transmitter end
  • H04L1/188—Time-out mechanisms
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/22—Traffic shaping
  • H04L47/225—Determination of shaping rate, e.g. using a moving window
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/34—Flow control; Congestion control ensuring sequence integrity, e.g. using sequence numbers
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/06—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information
  • H04W28/065—Optimizing the usage of the radio link, e.g. header compression, information sizing, discarding information using assembly or disassembly of packets
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04W—WIRELESS COMMUNICATION NETWORKS
  • H04W28/00—Network traffic management; Network resource management
  • H04W28/02—Traffic management, e.g. flow control or congestion control
  • H04W28/04—Error control

Definitions

• the present invention relates to radio link control (RLC) data transmission in a UMTS (universal mobile telecommunications system), and more particularly, to a method for moving a receive window in a radio access network.
• RLC radio link control
• FIG. 1 illustrates a structure of a radio interface protocol between a terminal and the UTRAN according to the 3GPP radio access network standards.
• a radio interface protocol has horizontal layers comprising a physical layer, a data link layer, and a network layer, and has vertical planes comprising a user plane for transmitting user data and a control plane for transmitting control information.
• the user plane is a region that handles traffic information of the user, such as voice and Internet protocol (IP) packets
• the control plane is a region that handles control information for an interface of a network, maintenance and management of a call, and the like.
• the protocol layers in FIG. 1 can be divided into a first layer (L1), a second layer (L2), and a third layer (L3) based on the three lower layers of an
• OSI open system interconnection
• the first layer (L1 ), namely, the physical layer, provides an
• the physical layer is connected to an upper layer
• MAC medium access control
• MAC layer and the physical layer send and receive data with one another via
• the second layer (L2) includes a MAC layer, a radio link control
• the MAC layer provides an allocation service of the MAC parameters
• the MAC layer is
• radio link control (RLC) layer connected to an upper layer called the radio link control (RLC) layer, via a RLC layer.
• RLC radio link control
• Various logical channels are provided according to the kind of
• the RLC layer supports reliable data transmissions, and performs a segmentation and concatenation function on a plurality of RLC service data units (RLC SDUs) delivered from an upper layer.
• RLC SDUs RLC service data units
• the RLC layer adjusts the size of each RLC SDU in an appropriate manner upon considering processing capacity, and then creates certain data units with header information added thereto.
• the created data units are called protocol data units (PDUs), which are then transferred to the MAC layer via a logical channel.
• the RLC layer includes a RLC buffer for storing the RLC SDUs and/or the RLC PDUs.
• the PDCP (Packet Data Convergence Protocol) layer allows the data transmitted through a network protocol (such as an IPv4 or IPv6) to be effectively transmitted on a radio interface with a relatively small bandwidth.
• a network protocol such as an IPv4 or IPv6
• the PDCP layer performs the function of reducing unnecessary control information used for a wired network, and this type of function is called, header compression.
• the RRC layer is defined only in the control plane, and handles the controlling of logical channels, transport channels, and physical channels with respect to setting, resetting, and releasing of radio bearers.
• the radio bearer service refers to a service that the second layer (L2) provides for data transmission between the terminal and the UTRAN, and in general, setting the radio bearer refers to defining the protocol layers and the channel characteristics of the channels required for providing a specific service, as well as respectively setting substantial parameters and operation methods.
• the PDCP and BMC layers exist in the user plane only, while the MAC and RLC layers can exist in the user plane or the control plane according to the upper layer connected thereto. Namely, when the RLC layer provides services to the RRC layer, the MAC and RLC layers exist in the control plane. Otherwise, they exist in the user plane.
• the other the second layers (excluding the MAC layer) have a plurality of entities to guarantee the QoS (quality of service) that is appropriate for each radio bearer (RB). Namely, a multitude of entities can exist in one layer, and each entity provides a separate service.
• the RLC layer will be explained in more detail as follows.
• a basic function of the RLC layer is to guarantee the QoS of each RB and their corresponding data transmissions.
• the RB service is a service that the second layer of the radio protocol provides to higher layers, the entire second layer affects the QoS, and in particular, the RLC layer has significant influence to the QoS.
• the RLC provides an independent RLC entity for each RB in order to guarantee the particular QoS of the RB, and provides three RLC modes, namely, a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (AM) to support various types of QoS.
• TM transparent mode
• UM unacknowledged mode
• AM acknowledged mode
• TM RLC transparent mode
• UM unacknowledged mode
• AM acknowledged mode
• each operational mode of the RLC must be considered in more detail.
• the particular RLC for each mode will be referred to as TM RLC, UM RLC, and AM RLC.
• TM In TM, employing a TM RLC, no protocol overhead is added to the RLC SDU that is transferred from higher layer. As the RLC lets the SDU pass "transparently," this mode is called transparent mode (TM). Accordingly, the user plane and the control plane perform the following functions. In the user plane, because a data processing time at the RLC is short, real-time circuit data transmissions (such as voice and streaming in the circuit service domain (CS domain)) are handled. In the control plane, because there is no protocol overhead within the RLC, uplink transmission of RRC messages from an unspecified terminal (UE), and downlink transmission of RRC messages that are broadcast to all terminals (UE) within a cell are handled.
• UE unspecified terminal
• UE unspecified terminal
• Non-transparent mode a mode in which protocol overhead is added at the RLC is called non-transparent mode.
• Non- transparent mode is divided into unacknowledged mode (UM) that has no reception acknowledgement for the transferred data, and acknowledged mode (AM) that has acknowledgement.
• UM employing a UM RLC
• a PDU header including a sequence number (SN) is added to each PDU and then transferred, in order to allow the receiving side to identify which PDUs were lost during transmission.
• SN sequence number
• the user plane handles broadcast/multicast data transmissions or real-time packet data transmissions, such as voice (e.g., VoIP) and streaming in the packet service domain (PS domain).
• voice e.g., VoIP
• PS domain packet service domain
• RLC entity exists at the reception side.
• the AM RLC requires a more complicated structure and data-
• AM RLC a re-transmission function
• transmission buffer is required in addition to a transmission buffer to manage
• the AM RLC performs various functions, such as using a "transmitting/receiving window” for flow control, performing "Polling" in which
• the transmitting side requests status information from a peer RLC entity at
• the AM RLC needs various protocol
• One of the main functions of a RLC is the SDU discard function
• the timer scheme is used in all three kinds of RLC modes (TM, UM, and AM).
• a transmitting side RLC entity operates a timer (e.g., a discard time) for measuring the time (duration) that each RLC SDU remains at the RLC layer, each RLC SDU being received from an upper layer. If a particular SDU fails to be properly transmitted upon expiration of time period set by the timer, that SDU is discarded and all SDUs between the beginning of a transmitting window and the corresponding SDU are discarded as well.
• a timer e.g., a discard time
• the limited number of re-transmissions scheme is used in AM RLC only. If the transmission and re-transmission of a particular RLC PDU continue to be unsuccessful and the maximum (limit) number of retransmissions is reached, a transmitting side RLC entity discards any SDU that includes at least a portion of the corresponding RLC PDU. This operation is described in more detail below.
• the RLC SDU transferred down to the AM RLC layer at the transmitting side is converted into a RLC PDU to be stored in a buffer.
• a counter e.g., VT (DAT)
• VT DAT
• the VT (DAT) is incremented by '1' each time the RLC PDU (that the VT (DAT) is responsible for) is transmitted.
• the transmitting side AM RLC discards at least one RLC SDU
• such a discard is notified to the receiving side AM RLC so that the receiving window of the receiving side is moved.
• the receiving window can be moved because the receiving side no longer needs to stand by and wait for the SDU that has now been discarded and thus would not be transmitted.
• this type of operation can be referred to as a 'Move Receiving Window (MRW)' function.
• the transmitting side sends an MRW message to the receiving side for moving the receiving window.
• the MRW command does not specify the location to which the receiving window should actually move to, but only provides information that a particular SDU has been discarded at the transmitting side.
• the receiving side Upon receiving the MRW message, the receiving side appropriately moves the receiving window based on the information of the discarded SDU.
• a procedure of moving a receiving window is called a MRW procedure.
• the MRW procedure includes the steps of transmitting a MRW command from the transmitting side, moving the receiving window by the receiving side and transmitting receiving window move information to the transmitting side, and moving the transmitting window at the transmitting side.
• the operation of each of these steps is explained in detail as follows. For better understanding, the explanation begins with the step performed by the transmitting side of receiving an SDU from a higher layer. Construction of PDU from SDU
• the transmitting side AM RLC performs segmentation and concatenation on the SDUs (which may be of different sizes) to construct an AM data (AMD) PDU having a predetermined size.
• the AMD PDU includes a header added to a payload.
• the payload consists of a portion of an SDU or at least one or more SDUs.
• the header consists of a sequence number (SN) of the PDU and a length indicator (LI) indicating the location of a boundary of the SDU if such boundary exists.
• FIG. 2 shows an example of how PDUs are constructed from SDUs.
• 39 th SDUs are shown. However, it can be understood that additional SDUs may continue to be delivered and that the AM RLC continues to construct additional PDUs for the descending SDUs. Furthermore, the AM RLC attaches the SN of the PDU to the AMD PDU header. If a boundary of the
• FIG. 3 is an exemplary diagram of showing the processing of the 21 st to 23 rd AMD PDUs among the constructed AMD PDUs in FIG. 2.
• the 21 st PDU consists of a portion of the 33 rd SDU (SDU 33), whereby no boundary of the 33 rd SDU (SDU 33) exists within the 21 st PDU.
• the 21 st PDU simply consists of an SN (in the header) and a portion of SDU 33.
• PDU consists of an end portion of SDU 33, the entirety of SDU 34, and a beginning portion of SDU 35, whereby two SDU boundaries exist within the
• Each constructed AMD PDU is stored in a transmission buffer of the AM RLC, and simultaneously stored in a re-transmission buffer for possible re-transmission that may take place at a later time.
• the difference between the transmission and re-transmission buffers lies in that the PDU having been transmitted once is removed from the transmission buffer, but is stored in the re-transmission buffer until that PDU is successfully transmitted.
• FIG. 4 shows an example of how the AM RLC constructs and stores the AMD PDU in the transmission and re-transmission buffers.
• the transmitting side AM RLC transmits the constructed PDUs to the receiving side AM RLC of the peer AM RLC entity.
• the transmitting side AM RLC transmits AMD PDUs
• all PDUs are not transmitted at once, as only those PDUs within a transmitting window can be transmitted.
• the reason that the AM RLC employs a transmitting window and a receiving window to transmit and receive PDUs is to manage those PDUs that need to be re-transmitted.
• the transmitting side only transmits those PDUs in the transmitting window, and the receiving side only receives those PDUs in the receiving window.
• a "window" represents a range of PDU SN values, whereby the PDUs in the receiving window refer to those PDUs having SN values within the range of PDU SN values corresponding to the receiving window.
• the transmitting side enables the transmission of only those PDUs having SNs within a range from the start point to the next-to-last end point ("endpoint-1").
• the PDUs having SNs at and after the end point can be transmitted only after the transmitting window is updated. Updating of the transmitting window takes place when the ACK for the first in-sequence PDU is received from the receiving side.
• the size of the transmitting window and the receiving window is defined as the interval (size) between the start point and the end point. For example, assuming that the size of the transmitting/receiving window is 10 and the 1 st to 20 th PDUs have been successfully transmitted, the range of the transmitting window is 21-31 , and also, the range of the receiving window is 21-31.
• the transmitting window can be updated only if the successful transmission of the 21 st PDU is confirmed.
• the receiving window can be updated only if the successfully receiving of the 21 st PDU is confirmed.
• the transmitting side can only transmit the 21 st to 30 th PDUs. Accordingly, the receiving side can only receive the 21 st to 30 th PDUs as well. The receiving side immediately discards any PDU having an SN that is out of range, as soon as such PDU is received. Updating of the transmitting window and the receiving window is continuously performed while the AMD PDUs are transmitted/received, as is shown in FIG. 5.
• PDUs up to the ,20 th PDU, are assumed to be successfully transmitted and both the transmitting window and the receiving window having a range of 21-31.
• the receiving side waits for PDU reception with a receiving window having a range between 21-31. For those PDUs within the range, proper reception is possible. However, if a PDU that is outside the range is received, the receiving side regards such PDU as erroneous and thus immediately discards such PDU. Since the transmitting side sequentially transmits PDUs, the receiving side sequentially receives these PDUs as well. The receiving side updates the receiving window to a range of 22-32 once the 21 st PDU is properly received. Thereafter, upon properly receiving the 22 nd PDU, the receiving side updates the receiving window to 23-33. Namely, updating of the receiving window takes place only if a PDU that is supposed to be received in-sequence is properly received.
• FIG. 5 shows an example where the 23 rd , 26 th , and 27 th PDUs are lost during transmission.
• the receiving side sends a status report regarding the received PDUs to the transmitting side.
• the status report is sent at the time when the 28 th PDU is received.
• the reported status information provides that among the 21 st to 28 th PDUs, the 23 rd , 26 th , and 27 th PDUs have not been properly received, and other PDUs have been properly received.
• the transmitting side Upon receiving the status report from the receiving side, the transmitting side deletes the successfully transmitted PDUs from the retransmission buffer, then updates the transmitting window, and prepares retransmission of the transmission-failed PDUs. Namely, after deleting the 21 st , 22 nd , 24 th , 25 th , and 28 th PDUs (i.e., the properly transmitted PDUs) from the re-transmission buffer, the transmitting side maintains the 23 rd , 26 th , and 27 th PDUs in the re-transmission buffer and prepares for re-transmission.
• the transmitting side maintains the 23 rd , 26 th , and 27 th PDUs in the re-transmission buffer and prepares for re-transmission.
• PDUs are additionally constructed (up to the 34 th PDU) after the PDUs (up to the 28 th PDU) have been properly transmitted.
• the 23 rd , 26 th , and 27 th PDUs are re- transmitted and then the 29 th to 32 nd PDUs are transmitted for the first time.
• the 33 rd and 34 th PDUs are outside the range of the transmitting window, they are stored in the transmission buffer and await subsequent transmission.
• FIG. 5 shows that the 27 th , 30 th , and 31 st PDUs are not received among the PDUs up to the 32 nd PDU. Specifically, the 27 th PDU failed to be transmitted twice (that is, one re-transmission failed).
• the receiving side assuming that the receiving side sends a status report, the receiving side having received the PDUs up to the 32 nd PDU will send a status report indicating the failure to receive the 27 th , 30 th , and 31 st PDUs. Discard of SDU
• the transmission failure of the 23 rd PDU means that the 35 th and 36 th SDUs will also have transmission failures.
• the discarding of SDUs differs for the timer scheme and for the limited number of re-transmissions scheme, thus these will be explained in more detail as follows.
• the AM RLC Upon receiving an SDU from a higher layer, the AM RLC immediately operates a discard timer for the SDU.
• the discard timer operates for each SDU.
• the discard timer stops operating the moment the SDU is successfully transmitted and the discard timer assigned to that SDU is removed (expires).
• 'successfully transmitted' means that an ACK signal (informing that all PDUs having at least a portion of an SDU have been successfully received) is received from the receiving side.
• the discard timer sequentially expires as well. In FIG. 2, if the 23 rd PDU is not successfully transmitted by the time the discard timer of the 35 th SDU expires, the 35 th SDU is discarded at the moment when the discard timer expires.
• the SDU is discarded, and not the PDU. Since a PDU is constructed with segmented and/or concatenated SDUs, one SDU may be entirely within one PDU or one SDU may span across several PDUs. In any case, the discard of the SDU means that all corresponding portions of the SDU are discarded from all PDUs that contain any portion of that SDU.
• the retransmission does not exclude the portion of the 35 th SDU.
• the construction of the re-transmitted PDU should be equal to that of the originally transmitted PDU.
• the discard method using the timer scheme performs the discard of SDUs using the expiration of the discard timer, by which the discard of SDUs occur sequentially.
• an SDU is discarded if the PDU that has been re-transmitted (as many times as the maximum (limit) number of re-transmission scheme allows) is not successfully transmitted.
• all SDUs including at least a portion of the corresponding PDU are simultaneously discarded according to the limited number of re-transmissions scheme.
• a MRW procedure that is directly related to the present invention is explained as follows. After discarding an SDU, the transmitting side AM RLC informs the receiving side of the discarded SDU through a MRW command for moving the receiving window.
• the MRW command does not directly indicate the position to which the receiving window should move, but only informs the SDU discard information, whereby the receiving side moves the receiving window to an appropriate position based on the discard information.
• the MRW command should include information related 'to which PDU the end portion of the SDU belongs' and 'to which portion in the PDU the end portion of the SDU belongs'.
• the MRW command consists of a SN of PDU to which the end portion of the discarded SDU belongs, and an indicator indicating an end of the discarded SDU in the PDU.
• the MRW command carries information about the last discarded SDU. This is because the position to which the receiving window has to move is located after the end of the last discarded SDU. Moreover, as explained in the foregoing description, when a certain SDU is discarded, all SDUs between the start point of the transmitting window and the corresponding SDU are discarded as well. Hence, the
• receiving side only receives the information of the last discarded SDU so as
• command can optionally inform such information.
• FIG. 6 is a conceptual diagram of the structure of a MRW command
• 'N' is the number of discarded SDU information that is carried by
• a basic MRW command contains information
• SDU 1 to SDU (N-1 ) can
• the uppermost field is the number of the PDU SNs included in the MRW command and is equal to 'N'. It is important to note that N is not the number of SDUs substantially discarded in the transmitting side, but the number of SDU discard information carried in the corresponding MRW command.
• the MRW command includes the SN of PDU where an end portion of the N th SDU exists, the MRW command includes one SDU discard information, such that the count is 1.
• the MRW command includes N SDU discard information so that the number is N.
• the reason why a value of N is notified is that the receiving side is informed whether optional SDU discard information of 1 ⁇ (N- 1 ) exists or not when receiving the MRW command. .
• indicator information that indicates where the end portion of the N th SDU is located within the PDU, is always included at the end of the MRW command. Referring to FIGs.
• the discard information of the 35 th SDU can be optionally inserted by a request of the higher layer and a count (number) field value of the uppermost PDU SN is correspondingly adjusted.
• the receiving side Upon receiving a MRW command, the receiving side discards all SDUs from an SDU existing at a start point of a receiving window to a last SDU informed by the MRW command, and correspondingly moves the receiving window.
• the moved position of the receiving window varies according to whether the PDUs (that include the SDUs after the discarded SDU) are received or not.
• the basic principle is that the start point of the receiving window is moved to the SN of the PDU that is first received in-sequence after excluding the discarded SDUs.
• the moved position of the receiving window may be the PDU that includes an end portion of the last discarded SDU informed by the MRW command or the PDU that follows after subsequent PDUs have been successfully received.
• the receiving side consecutively discards the SDUs from the start point of the receiving window to correspond to the MRW command, moves the receiving window, and then informs the transmitting side of the moved position of the receiving window.
• the start point of the receiving window is the SN of the PDU to be first received in-sequence.
• the moved position of the receiving window is explained by reference to the MRW command in FIG. 7 as an example.
• the receiving side successfully receives all PDUs up to the 22 nd PDU, but fails to receive the 23 rd PDU, whereby the start point of the receiving window is the 23 rd PDU.
• the receiving side discards all the SDUs from the start point of the receiving window up to the last discarded SDU.
• the position of the receiving window may already proceed further than the PDU specified by the MRW command.
• Such a situation occurs when the ACK information is lost during transmission, even if the receiving side having properly received the PDU sends the ACK information to the transmitting side.
• the receiving side successfully received the PDU and correspondingly updated the receiving window.
• the transmitting side fails to receive ACK information for the transmitted PDU, thereby failing to update its receiving window.
• the start point of the receiving window is behind the start point of the transmitting window.
• the receiving side successfully received all the PDUs up to the 28 th PDU and updated the start point of the receiving window to the 29 th PDU.
• the ACK information for the 23 rd PDU is consecutively lost during transmission, whereby the start point of the transmitting window may be held at the 23 rd PDU.
• the transmitting side discards the 35 th and 36 th SDUs, and transmits the SDU discard information to the receiving side, the SDU discard information is of no use, because the receiving window of the receiving side has already been moved to the 29 th PDU.
• the receiving side ignores this information and informs the transmitting side of a current position of the receiving window. Yet, the receiving side may not discard the SDU that was discarded by the transmitting side. Namely, if the discard information for the SDU that was successfully received and delivered to the higher layer is received, the corresponding SDU cannot be discarded because the corresponding SDU was already delivered to the higher layer. The receiving side may only inform the higher layer of the information that the corresponding SDU was discarded in the transmitting side. Transmitting Window Move
• the transmitting side moves the start point of the transmitting window to the
• transmitting side starts to transmit from the corresponding PDU.
• receiving side discards all SDUs from the start point of the receiving window
• FIG. 8A is a diagram of explaining how a discontinuous SDU discard
• the start points of transmitting and receiving windows may be
• FIG. 8A is a diagram of transmitting the 21 st to 28 th PDUs from the transmitting side.
• the PDUs up to the 30 th PDU can be substantially transmitted.
• the SDUs are sequentially delivered down to
• the receiving side fails to receive the 23 rd , 26 th , and 27 th PDUs among the 21 st to 28 th PDUs transmitted through the above-described process, because of losses during transmission and succeeds in receiving the rest of the PDUs.
• the receiving side updates the start point of the receiving window to the 23 rd PDU. Yet, no additional receiving window updating takes place since the 23 rd PDU has not been received.
• the transmitting side deletes the 21 st , 22 nd , 24 th , 25 th , and 28 th PDUs from a buffer, updates the start point of the transmitting window to the 23 rd PDU, and then awaits subsequent transmission.
• FIG. 8B is a diagram explaining a procedure of the transmitting side for updating the transmitting window to 23-33, and then performs subsequent transmission.
• the PDUs are transmitted in order of the 23 rd .
• PDUs require re-transmission. It should be noted that even though the PDUs from the 33 rd PDU are constructed, they cannot be transmitted due to the size limitation of the transmitting window.
• the receiving side still fails to receive the 23 rd and 27 th PDUs among the transmitted 23 rd to 32 nd PDUs, and further fails to receive the 30 th and 31 st PDUs. Since the 23 rd PDU is not received, the receiving window, a shown in FIG. 8B, maintains its current range of 23-33.
• the transmitting side deletes the PDUs succeeding in transmission from the buffer. Yet, since the ACK for the 23 rd PDU is not received, updating of the transmitting window fails to take place like in the receiving side. Hence, the transmitting side, as shown in FIG. 8C, retransmits the 23 rd , 27 th , 30 th , and 31 st PDUs while maintaining the transmitting window at a range of 23-33.
• the transmitting side fails to transmit additional PDUs, and only retransmits the 23 rd and 27 th PDUs. Thereafter, assuming that 23 rd and 27 th PDUs continue to be re-transmitted, but ultimately fail to be properly transmitted, the transmitting side then discards the corresponding SDUs due to the discard timer expiration for SDU or the maximum (limit) number of retransmissions has been reached.
• the transmitting side regards the 35 th and 36 th SDUs as one set, and the 38 th and 39 th SDUs as another set, and then performs the MRW procedure on each of the two sets. Since the MRW procedures are performed one-by-one at any one moment, they cannot be simultaneously executed but is sequentially executed one after the other. Such a procedure is explained in more detail by referring to FIG. 10.
• the transmitting side executes a first MRW procedure while the transmitting window is between 23-33.
• the transmitting side discards all SDUs from the start point of the transmitting window to the 36 th SDU, and transmits such information to the receiving side using a MRW command (S1 , S2).
• the receiving side discards all SDUs from the start point of the receiving window to the last discarded SDU informed by the received MRW command, i.e., the 36 th SDU, and then moves the receiving window to 27-37 (S3).
• the receiving side informs the transmitting side of a moved position of the receiving window (S4).
• the transmitting side then terminates the first MRW procedure and moves the transmitting window to 27-37 in order to correspond with the moved position of the receiving window.
• the transmitting side then executes a second MRW procedure to move the receiving window after the 39 th SDU (S5).
• Another MRW command transmitted in the second MRW procedure includes the discard information of the 39 th SDU that is the last discarded SDU of a second discontinuous discarded SDU set.
• the 33 rd to 36 th PDUs can be transmitted (S6). After discarding all the SDUs from the start point of the receiving window to the last discarded SDU informed by the received MRW command, i.e., the 39 th SDU, the receiving side moves the start point of the receiving window to an "appropriate" position between 33-37 (S7).
• the 33 rd to 36 th PDUs can be transmitted while the second MRW procedure is performed, whereby the position of the receiving window is referred to as being "appropriate” because such position varies depending upon whether these PDU are received.
• the receiving window is updated to 33-43. If all of the 33 rd to 36 th PDUs are received, the receiving window is updated to 37-47.
• the transmittable PDUs can be transmitted during the MRW procedure, whereby the reception of such PDUs changes (updates) the position of the receiving window. This is the same as in the first MRW procedure. Yet, since there are no transmittable PDUs except the 23 rd and 27 th PDUs between the range of 23-33 of the receiving window in the example of FIG. 8, the start point of the receiving window was defined as 27.
• the receiving side After moving the start point of the receiving window to the appropriate position, the receiving side transmits transmitting window move information to the transmitting side (S8).
• the transmitting side having received the transmitting window move information terminates the second MRW procedure and moves the start point of the transmitting window to correspond with that of the receiving window (S9).
• the transmitting window is then used to continue transmission from the PDU at the start point of the transmitting window (S 10).
• FIG. 11 is a flowchart of moving a receiving window using this method (method B) when the discontinuous SDU discard as shown in FIG. 9 takes place.
• the transmitting side discards all SDUs from one SDU corresponding to the start point of the transmitting window up to the last one of the discarded SDUs, regardless of transmission success or failure such that the SDUs from the start point of the transmitting window up to last SDU are continuously discarded. Namely, if the SDUs are discontinuously discarded as shown in FIG. 9, the transmitting side discards all SDUs from the 35 th SDU of the start point of the transmitting window up to the 39 th SDU of the last discarded SDU, and sends such information to the receiving side (S11 , S12). In this case, the 37 th SDU is discarded despite succeeding in transmission.
• the receiving side informs the transmitting side of the moved position of the receiving window (S14).
• the transmitting side having received the moved position terminates the MRW procedure and moves the transmitting window to 33-44 (S15).
• the transmitting side then starts transmission from the 33 rd PDU of the start point of the transmitting window (S16).
• the receiving window is moved by using one of the two methods, methods A or B in the related art.
• the related art methods A and B have the following problems or disadvantages.
• the receiving side discards the SDUs that were successfully transmitted as well, which undesirably reduces transmission efficiency. Namely, in the example of FIG. 9, only the 37 th SDU is unnecessarily discarded, and thus the transmission efficiency is not greatly reduced. However, in other extreme examples, if the SDUs corresponding to the start and end points of the transmitting window are discarded, all SDUs in the transmitting window are discarded, which significantly reduces transmission efficiency.
• the present invention is directed to a method of moving a receiving window in a wireless mobile communication system that substantially obviates one or more problems due to limitations and disadvantages of the related art.
• a data communication method includes, receiving a move receiving window (MRW) command; and delivering successfully received service data units (SDUs) among data units from a start point of a current receiving window to a position indicated by the MRW command to an upper layer.
• MRW move receiving window
• SDUs successfully received service data units
• the MRW command is transmitted through a radio environment.
• the data units are service data units (SDUs) of a data link layer.
• SDUs service data units
• the data units are radio link control (RLC) SDUs.
• the SDUs are identified by a SDU boundary indicator.
• the SDU boundary indicator is included in a protocol data unit (PDU) of a data link layer.
• the SDUs that are not yet successfully received are discarded.
• the position that is indicated by the MRW command indicates an end point of the SDU to be discarded last.
• the steps are performed in a receive-response mode.
• the MRW command includes a sequence number of a protocol data unit (PDU) with an end point of the SDU discarded last; and an end point indicator indicating the end point of the SDU in the PDU.
• PDU protocol data unit
• the method further comprising moving the receiving window to the position indicated by the MRW command.
• the moving of the receiving window is performed in a data link layer.
• a method for moving a receiving window in a wireless mobile communication system includes receiving an information of a last discarded service e data unit (SDU) from a transmitting side; checking whether the SDUs prior to the last discarded service data unit are successfully received; and delivering the SDUs that are successfully received to a upper layer and moving a receiving window in accordance with the information.
• SDU last discarded service e data unit
• the SDU is a radio ling control (RLC) SDU.
• the information for the last discarded SDU includes a sequence number of a protocol data unit (PDU) with an end point of the SDU discarded last; and an end point indicator indicating the end point of the SDU in the PDU.
• PDU protocol data unit
• the moving of the receiving window is performed in a data link layer.
• the receiving window moves to the PDU including the end point of the last discarded SDU.
• the SDUs are identified by the end point indicator
• the checking step comprises identifying data from a portion indicated by one SDU end point indicator to a portion indicated by an adjacent SDU end point indicator as one SDU; and judging the corresponding SDU as successfully received if all portions of the identified
• FIG. 1 illustrates a block diagram of an architecture of a radio
• FIG. 3 is a diagram of explaining the 21 st to 23 rd AMD PDUs among
• FIG. 4 is a diagram showing how the AM RLC constructs an AMD
• FIG. 5 is a diagram of an example for transmitting/receiving AMD
• FIG. 6 is a diagram of a concept of a construction of a MRW
• FIG. 7 is a diagram of a MRW command format
• FIGs. 8A to 8C are diagrams of explaining how inconsecutive SDU
• FIG. 9 is a diagram of an example of discarding SDUs discontinuously.
• FIG. 10 is a flowchart of a process for moving a receiving window
• FIG. 11 is a flowchart of a process for moving a receiving window using a second method according to a related art when discarding SDUs discontinuously; and FIG. 12 is a flowchart of a method for moving a receiving window according to the present invention when discarding SDUs discontinuously.
• the present invention is implemented in a mobile communication system such as a UMTS (universal mobile telecommunications system) developed by the 3GPP.
• UMTS universal mobile telecommunications system
• the present invention is further applicable to communication systems operating under other standards.
• the AM RLC of the transmitting side transfers information of the last discarded SDU regardless of the continuity of the discarded SDUs.
• the AM RLC of the receiving side checks whether to receive the SDUs from the start point of the receiving window to the last discarded SDU, respectively, and delivers the SDUs that are successfully received to an upper layer, resulting in minimal time delay and minimal reduction of transmission efficiency even if discontinuous SDU discarding take place.
• a detailed embodiment of the present invention is applied to the case where SDUs are discarded according to FIG. 9. In this case, it is assumed that the PDU transmitting/receiving process is already in progress described with respect to Figs. ⁇ A to 8C.
• FIG. 12 is a flow chart of a method for moving a receiving window according to the present invention when discarding SDUs discontinuously.
• RLC executes a MRW procedure, and then adds to the MRW command, information of the 39 th SDU that is the last one of the discarded SDUs for transmission to the receiving side RLC (S20, S21).
• the transmitting window lies between the 23 rd PDU and the 33 rd PDU.
• the receiving side Upon receiving the MRW command, the receiving side extracts the discard information of the SDU located at a last position in the SDU discard information carried on the MRW command. By checking a first PDU SN count field, the portion of the information of the last discarded SDU can be obtained.
• the receiving side recognizes the information that the transmitting side discarded SDUs up to a first portion of the 28 th PDU.
• the receiving side checks all PDUs from the 23 rd PDU as the start point of the receiving window up to the 28 th PDU informed of by the MRW command to determine whether the SDUs are correctly received, and then selectively discards certain SDUs (S22).
• the receiving side determines which SDUs have been successfully received by using a boundary indicator, namely, a length indicator (LI) included in a PDU header.
• a boundary indicator namely, a length indicator (LI) included in a PDU header.
• the receiving side regards a portion between two neighboring Lls to be one SDU. If there is a portion of a different SDU between two Lls, the receiving side determines the corresponding SDU as a failure. In one embodiment of the present invention, as the receiving side receives PDUs in the same manner that shown in FIG. 9, the 23 rd and 27 th PDUs are not received. Hence, the receiving side determines as follows.
• the receiving side Failing to receive the 23 rd PDU, the receiving side considers (recognizes) the latter portion of the 22 nd PDU up to a beginning portion of the 25 th PDU as one SDU. Since a portion corresponding to the 23 rd PDU of the recognized SDU fails to be received, the receiving side discards it. The receiving side determines that a following portion corresponding to the 37 th PDU is successfully received and such is not discarded. Also, the receiving side recognizes the beginning portion of the 26 th PDU up to a beginning portion of the 28 th PDU as one SDU. The recognized SDU is discarded because a portion corresponding to the 27 th PDU has not been properly received. It is important to note that the receiving side differs from the transmitting side in calculating the total number of the discarded SDUs, if the
• MRW command only includes the information of the last discarded SDU.
• the transmitting side discards four SDUs in the example of FIG. 9. Yet, the receiving side regards that only two SDUs are discarded.
• the AM RLC is configured such that the information of all discarded SDUs is or is not delivered by the MRW command. If the RLC is set up to deliver the all discarded SDUs information, the transmitting side carries information about each of the discarded SDUs. In this case, the receiving side knows that the end portions of the discarded SDUs exist in the 23 rd , 25 th , 27 th , and 28 th PDUs, respectively, whereby it can be seen that four SDUs are discarded in the transmitting side.
• the MRW command does not directly deliver the number of the discarded SDUs, but rather, the SN of the PDU having the end portion of the discarded SDU. This is to inform the receiving side of a position of the discarded SDU. Namely, in the example of FIG. 9, the receiving side considers that two SDU groups including portions of the 35 th and 36 th SDUs, and the other portions of the 38 th and 39 th SDUs are discarded. If the end portions of each of the discarded SDUs in not informed, but the number of the discarded SDUs is informed, the receiving side is unable to know how many discarded SDUs exist in the front and the rear portions.
• the receiving side may consider that one SDU in the front portion, and three SDUs in the rear portion are discarded or that there are two discarded SDUs in each of the front and rear portions. This is related to a sequence of the discarded SDUs. The discard sequence is significant to some higher layers. Hence, the MRW command informs the PDU SN indicating where the end portion of each of the discarded SDUs exists.
• the receiving side discards portions corresponding to the 35 th , 36 th , 38 th , and 39 th SDUs, and delivers the 37 th SDU to an upper layer. Also, the RLC of the receiving side moves the start point of the receiving window to the 33 rd PDU to be first received in-sequence.
• the receiving side sends information of the start point of the moved receiving window to the transmitting side (S23).
• the transmitting side having received such information, determines that the MRW procedure is successfully performed, moves the transmitting window to the same position as that of the receiving window, and then initiates a subsequent PDU transmission (S24, S25).
• One embodiment of the present invention provides, in a radio access network, a method of discarding service data units by a sending end employing a transmission window and a discard trigger.
• the method can comprise the steps of, checking all service data units beginning with a first service data unit located at a lower edge of the transmission window up to a final service data unit that was discarded by the discard trigger, and discarding those checked service data units that have not been positively acknowledged.
• the above method can further comprise a step of sending, to a receiving end, a command to move a reception window and information of the final service data unit.
• this method can further comprise a step of acknowledging, to a sending end, any service data units that have been successfully received.
• the receiving side of the present invention checks whether all SDUs from the start point of the receiving window up to the last discarded SDU are successfully received, then delivers the SDUs that are successfully received to an upper layer, and discard only the SDUs that are not successfully received.
• a method of moving a receiving window according to the present invention overcomes the SDU transmission time delay problems created by moving the receiving window according to the related art, even if the SDUs are discontinuously discarded.
• the present invention overcomes the reduction of SDU transmission efficiency created by the related art method B, thereby enabling improved high-speed data communications, as well as maximizing data transmission efficiency.

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